Inclusion Criteria:

- 1. Has given written informed consent. 2. Has histologically and/or cytologically
proven unresectable or recurrent NSCLC stage IIIB with pleural effusion or
pericardial effusion, or stage IV (mixed forms with small cell lung cancer are
excluded).

3. Has received prior 1st line chemotherapy combination (platinum or
non-platinum-based) treatment and has not received any 2nd line therapy.

4. Has measurable disease as defined by Response Evaluation Criteria in Solid Tumors
(RECIST) criteria, ie, has at least one measurable lesion. A measurable lesion is one
that can be accurately measured in at least one dimension with the longest diameter ≥
20 mm using conventional techniques or ≥ 10 mm using spiral Computed Tomography (CT)
scan.

5. Is able to take medications orally. 6. Is ≥ 18 years of age. 7. Has an ECOG
performance status 0 or 1. 8. Has adequate organ function as defined by the following
criteria:

1. AST (SGOT) and ALT (SGPT) ≤ 2.5 x ULN; if liver function abnormalities are due
to underlying liver metastasis AST (SGOT) and ALT (SGPT) ≤ 5 x ULN.

2. Total serum bilirubin of ≤ 1.5 x ULN.

3. Absolute granulocyte count of ≥ 1,500/mm3.

4. Platelet count ≥ 100,000/mm3.

5. Hemoglobin of ≥ 9.0 g/dL.

6. Calculated creatinine clearance (CrCl) ≥ 60 mL/min (Cockcroft-Gault formula). 9.
Is willing and able to comply with scheduled visits, treatment plans, laboratory
tests, and other study procedures.

Exclusion Criteria:

- 1. Has had treatment with any of the following within the specified time frame prior
to study drug administration:

1. Any investigational agent either concurrently or within the past 30 days.

2. Any prior 1st line treatment with S-1 for NSCLC.

3. Previous therapy for NSCLC within the past 21 days, including any chemotherapy,
immunotherapy, biologic or hormonal therapy (6 weeks for nitrosureas or
mitomycin C).

4. Radiotherapy within the prior 2 weeks.

5. Any radiation therapy to a target lesion within the past 3 months, unless there
was evidence of PD after radiotherapy (and this target lesion must not be the
only site of measurable disease).

6. Current enrollment in another clinical study with an investigational agent.
Patients participating in surveys or observational studies are eligible to
participate in this study.

2. Has a serious illness or medical condition(s) including, but not limited to,
the following:

1. Other active malignancies.

2. Symptomatic brain metastasis not controlled by corticosteroids.

3. Leptomeningeal metastasis.

4. Myocardial infarction within the last 6 months, severe/unstable angina,
congestive heart failure New York Heart Association (NYHA) class III or IV.

5. Chronic nausea, vomiting, and/or diarrhea.

6. Psychiatric disorder that may interfere with consent and/or protocol compliance.

7. Known human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome
(AIDS)-related illness.

8. Other severe acute or chronic medical or psychiatric condition or laboratory
abnormality that may increase the risk associated with study participation or
study drug administration, or may interfere with the interpretation of study
results, and in the judgment of the Investigator would make the patient
inappropriate for entry into this study.

3. Is receiving concomitant treatment with drugs interacting with S-1. The
following drugs are prohibited because there may be an interaction with S-1:

1. Sorivudine, uracil, cimetidine, folinic acid, and dipyridamole (may enhance S-1
activity).

2. Allopurinol (may diminish S-1 activity).

3. Phenytoin (S-1 may enhance phenytoin activity).

4. Flucytosine, a fluorinated pyrimidine antifungal agent (may enhance S-1
activity).

4. Is a pregnant or lactating female. 5. With reproductive potential and refuses
to use an adequate means of contraception (including male patients).